1. Field of the Invention
The present invention relates to a lens mount for a CCTV (closed-circuit television) in which the lens is attached to a camera body by a threaded mount (hereinafter referred to as a screw mount), and more precisely, it relates to a mount shift apparatus in which the positional relationship between the optical axis and a light receiving surface of an image pickup device (CCD) can be adjusted when the lens is attached to the camera body.
2. Description of the Related Art
A lens mount for a CCTV camera is generally made of a screw mount such as a C-mount or CS-mount. In a screw mount, the center axis of the thread of the mount frame of the lens mount may deviated from the center of the optical system (optical axis) due to the screw engagement or screw fitting. Similarly, the center axis of the thread of the body mount may deviated from the center axis of the CCD which defines the light receiving surface. Consequently, when the lens is attached to the camera body, the center axis of the light receiving surface (light receiving surface center) is displaced from the optical axis. The deviation or displacement, which varies depending on the camera, is generally approximately within .+-.0.3 mm.
The deviation is not serious in a monitoring system using a CCTV. However, if the CCTV were used for a measurement in an image processing system, the deviation of the light receiving surface center from the optical axis makes a precise measurement impossible. Moreover, in the case of a fish-eye lens (all sky lens) which covers a view angle of 180.degree., a circular image formed by the fish-eye lens may be eclipsed.
There are known adjusting mechanisms which control the posture of the lens in the direction of rotation to mount the screw mount using a securing or set screw, etc. However, there is no know apparatus which corrects the deviation between the light receiving surface center and the optical axis in two orthogonal directions in a plane perpendicular to the optical axis.